1. The Field of the Invention
This invention relates to identification cards (I.D. cards) and more particularly to plastomeric protective materials for such cards.
2. Description of the Prior Art
I. D. cards are by now, well known articles of commerce. Many employ photographs containing information pertaining to the bearer and/or issuer and oftentimes the photographs are color diffusion transfer photographic products. In many instances, the photographs are protected by plastomeric sheet materials which are bonded, through appropriate adhesives, to one surface of the plastomeric protective sheet material. I. D. cards of this type are described in detail in U.S. Pat. Nos. 3,313,052; 3,498,788; 3,511,655; 3,582,439; 3,614,839 and 3,644,116 among others.
In I. D. cards of the type described above, the art especially prefers that a "security seal" be provided between the photograph and the surface of the protective plastic bonded to it. As those in the art know, the achievement of an effective "security seal" is best evidenced by attempts to remove the protective plastomeric sheet material from the photograph. If a security seal exists, all or at least portions of the image containing layer will be removed with the sheet material thereby evidencing the intrusion or attempted intrusion into the card.
A commercially available I. D. card which uses a protective plastomeric sheet material providing a "security seal" between the photograph and material is known in the art as the "PolaPouch" I. D. card. Details relating to elements of a "PolaPouch" I. D. card may be found in referenced U.S. Pat. Nos.3,582,439 and 3,614,839 and especially in the discussions there of the embodiments of FIGS. 2 and 3 of these patents. Essentially, such I. D. cards are prepared by simultaneously photographing a subject and relevant information for the card to provide a developed diffusion transfer I. D. photograph. While moist, the surface of the photograph is laminated to a clear plastomeric sheet material; the sheet material usually employed commercially comprises a cellulose acetate butyrate sheet material having on one surface, a security seal adhesive system comprising a layer of polyvinyl alcohol bonded to the cellulose acetate butyrate material through intermediate layers of cellulose nitrate and cellulose nitrate/hydrolyzed polyvinyl alcohol. Details relating to such cellulose acetate butyrate sheet materials may be found in U.S. Pat. Nos. 2,362,580; 2,541,478 and 2,835,609.
After lamination, the protective plastic material is trimmed to the shape and size of the photograph and then inserted into a polyvinylchloride pouch usually sealed about three edges. After insertion, the remaining open end(s) is sealed to provide the finished I. D. card.
Another commercially available I. D. card which uses a protective plastomeric providing a "security seal" is known in the art as the "Dual Bond" I. D. card. Details relating to a "dual Bond" I. D. card may also be found in U.S. Pat. Nos. 3,582,439 and 3,614,830 and especially in the discussion there of the embodiments of FIGS. 5 and 6. Essentially, "Dual Bond" I. D. cards employ a precut envelope comprising front and back sheet members coupled together along one edge so that the members can be easily separated for insertion of the photograph between them. The back sheet member is usually opaque and has a pressure sensitive adhesive coated on the inside surface. The front sheet member is transparent and comprises the cellulose acetate butyrate sheet material and the security seal adhesive system discussed before. After development and while the surface of the photograph is moist, the diffusion transfer photograph is positioned between the members of the envelope and pressure applied to effect lamination, the wet surface of the photograph being bonded to the polyvinyl alcohol layer carried by the transparent cellulose acetate butyrate sheet material.
It should be understood that in both the "PolaPouch" I. D. card and the "Dual Bond" I. D. card, the primary security feature is the security seal established between the photograph and the protective plastomeric sheet material. Accordingly, it is important that the seal between the surfaces be achieved at the instant of lamination or as shortly thereafter as possible and at least before the assembled card is presented to the intended bearer. With many present commercial I. D. issuance systems, for example, the time between photographing the subject and issuance of the finished card can average about ten minutes or slightly more or less. In the described commercial I. D. issuance systems, the cellulose acetate butyrate protective sheet material described above has successfully provided the desired performance characteristics required by the art especially in terms of the excellent adherent properties of the bond or seal achieved and the time required to achieve it. A large measurwe of this success is due most likely to a distinctive affinity between the particular materials comprising the surface of the photograph containing the image and the above described elements of the security seal adhesive system integrated with the described protective sheet material.
As mentioned, a number of commercial I. D. issuance system employ diffusion transfer film units which provide a color I. D. photograph. The film units so employed are sold by Polarioud Corporation and are designated as Polaroid Land Type 108 film. Essentially, such film units comprise a photosensitive element that can provide an imagewise distribution of diffusible dye-image providing materials after exposure and after distribution of processing composition between the photoexposed element and a superposed image-receiving element. After development, the photosensitive element and image-receiving element are stripped apart and the image is viewed in the image receiving layer of the image receiving element. In Type 108 film, the image receiving layer comprises a mixture of polyvinyl alcohol and poly-4-vinyl pyridine and this layer, when moist, can be bonded to the cellulose acetate butyrate sheet material described before to provide a security seal which corresponds very closely to idealized performance characteristics.
Recently, another diffusion transfer film unit sold by Polaroid Corporation and designated as Polacolor II has become available for use in commercial, instant I. D. issuance systems. Although different dye image providing materials are employed in Type 108 and Polacolor II film, the essential difference between Type 108 and Polacolor II film units insofar as the achievement of a security seal is concerned resides in a difference between the image receiving layers of the films. Like the image receiving layer of Type 108 film, the image receiving layer of Polacolor II also comprises a mixture of polyvinyl alcohol and poly:4-vinylpyridine. However, the image receiving layer of the Polacolor II film additionally comprises a stripping layer formed by coating a solution of ammonia and a hydrophilic colloid (usually gum arabic) on the image receiving layer containing the mixture of polyvinyl alcohol and poly-4-vinylpyridine. Details relating to this overcoated layer can be found in commonly assigned, copending application Ser. No. 584,488 filed June 6, 1975, now U.S. Pat. No. 4,009,031. Although the differences between the image-receiving elements of the described film units is only in the stripping layer, apparently a residue thereof remains after stripping and is sufficient to affect the quality of security seal achieved in bonding the cellulose acetate butyrate protective sheet material of the prior art to Polacolor II diffusion transfer photographs.
The present invention is addressed to the problems discussed above regarding security seals and presents to the art novel, improved plastomeric protective sheet materials which can provide superior security seals for a wider range of diffusion transfer which photographs than can be achieved by the protective materials of the prior art.